Hi,
I’m trying to sign an existing PDF with libre office: File → Digital Signatures → Sign existing PDF;
Then I click on the Sign Document button, and again on the Sign Document button in the Digital Signatures dialog;
Select certificate dialog pop-out and I select my certificate and click sign.
After that nothing happens. There is no dialog to enter the pin.
However, the pin is asked for when I try to sign a LibreOffice document, such as an odt document.
Edit: This is on Windows 10. I used to be able to sign pdfs in previous versions of libreoffice.